Programmable infusion pumps are used to carry out controlled delivery of liquid food for enteral feeding and medications for various purposes such as pain management. In a common arrangement, an infusion pump receives a disposable administration set comprising flexible tubing having a tubing segment designed to be engaged by a pumping mechanism of the infusion pump. The administration set may further comprise a pair of mounting components fixedly attached to the flexible tubing at predetermined locations at or near opposite ends of the tubing segment, whereby the mounting components are receivable by respective mating features on the infusion pump to secure the tubing segment in proper position for operative engagement by the pumping mechanism. One of the mounting components may provide additional functionality beyond helping to properly locate the tubing segment. For example, one of the mounting components may be configured as a free-flow protection device operable to selectively stop and permit flow of the infusion liquid through the tubing. Upon loading the administration set in the pump, the free-flow protection device is actuated from its normal flow-stopping closed position to its open position allowing flow. An example of the arrangement described above is disclosed in U.S. Pat. No. 6,164,921 to Moubayed et al.
In prior art arrangements, a door or platen member of the pump pivots into a closed position after the administration set is loaded. During closure, the door or platen member actuates the free-flow protection device from its closed position to its open position. For example, the free-flow protection device may include a valve body and a plunger spring-biased to pinch the tubing closed, and the door or platen member may engage the plunger and move the plunger against the spring bias to open flow in the tubing. Once the door or platen member is fully closed, the pumping mechanism takes over for the opened free-flow protection device to prevent unintended flow through the tubing.
With this type of arrangement, the free-flow protection device begins to open before the door or platen member is completely closed, and before the pumping mechanism can prevent flow. Consequently, there is a risk that liquid may be infused into the patient by gravity rather than by programmed action of the pumping mechanism when the door or platen member is slightly ajar.